The increase in fossil fuel consumption coupled with the diminishing supply of these resources have given rise to the implementation of electric drive machines. These machines may be designed to provide combinations of electric and/or internal combustion power to the machines' drive train to reduce fuel consumption. In some configurations, an engine powers a generator, which provides electric power to a battery system and an electric motor. Typically, the electric motor is configured to drive the wheels or travel mechanisms of the work machine (e.g., sprockets on a track type tractor, etc.). Other types of electric drive machines allow both an engine and electric motor to provide power to the travel mechanisms of the work machine.
The evolution of electric drive machines have also given rise to new types of systems for controlling the power produced by the electric motor and/or engine. Typically, conventional control systems for electric drive machines use various machine operating conditions and parameters to adjust the operations of the machine's engine and/or electric motor in an attempt to increase the performance efficiency of the work machine.
Although conventional systems may control an engine in an electric drive machine, such control is based on anticipated changes to the work loads experienced by the vehicle. Accordingly, these systems may require extensive processing capabilities to determine the appropriate adjustments to be made to the operation of the engine to offset the loads experienced by the machine's motor. Such processing is sometimes not feasible in working environments where a work machine performs repeated motions that require many directional shifts and speed fluctuations. To reduce losses experienced by a work machine in such conditions, some control systems have been developed that take into account machine speed or directional fluctuations. One such system is described in U.S. Pat. No. 5,725,064 (“the '064 patent”), which uses a control system to cut off the fuel supply of an electric drive machine's engine when the machine is in reverse, when an auxiliary component is running during idle conditions, or when the motor is exclusively used to drive the machine. The control system in the '064 patent decompresses the engine following its shut down to reduce engine pumping losses. This reduces drag on the motor that may result from the shut down of the engine.
Although the system described in the '064 patent uses a control system to increase the efficiency of an electric drive machine, it does so in a manner requiring the engine to be shut down. Thus, the vehicle relies on the electric motor for mobility while in reverse. Further, the '064 patent, as well as other conventional electric drive control systems, do not consider overspeed limit conditions during directional shifts. Accordingly, there is a need for an electric drive control system that controls an engine based on directional shifts without complex processing or drastic mechanical changes in order to increase fuel efficiency and overspeed limit capabilities during certain directional shift conditions.
Methods, systems, and articles of manufacture consistent with the disclosed embodiments are directed to solving one or more of the problems set forth above.